Dabigatran etexilate of formula II
is an oral direct thrombin inhibitor useful in the prophylaxis of thromboembolism in patients undergoing total knee or hip replacement and also suitable for the prevention of stroke, in particular in patients with atrial fibrillation. Although clinical monitoring of dabigatran etexilate is not required, a reliable laboratory method to measure the pharmacodynamic effects of dabigatran etexilate would be useful. Such a method could be used not only to monitor the kinetics of the drug activity in the body but also to adjust dosing and posology of the drug. Via such a method drug concentration in the patient's blood could be determined which could be useful to avoid overdosing. Therefore, it is the general object of the invention to provide for an assay that is useful to analyse the pharmacodynamic effects of dabigatran etexilate.